The field of the present invention is motor driven speed reduction devices.
Motors with speed reduction devices for low speed and high torque applications have typically employed a combination of a motor with an output shaft protruding axially and a speed reduction device contained in its own case. A pinion gear is typically mounted to the shaft of the motor and is engaged with gearing inside the case. The appropriate ratio is achieved by changes in the ratio of gear teeth and in an increase or decrease in the number of gear wheels.
A conventional motor driven gear reduction mechanism is illustrated in FIG. 1. A cylindrical motor housing 1 mounts an inductive stator 2. Concentrically arranged inwardly of the stator 2 are permanent magnets 4 mounted to a rotor 5. The rotor 5 is rotatably mounted within the housing 1 by means of an output shaft 6. The output shaft 6 has a pinion gear 7 mounted at one end thereof outwardly of the housing 1.
The pinion gear 7 is engaged with a gear including gear wheels 8, 9 and 10. The gear wheels 8 and 9 are fixed on a common shaft 11. The gear wheel 10 is fixed on an output shaft 12. Thus, the motor provides torque to the gear reduction device which in turn, through the gear, provides a high torque reduced speed output through the shaft 12.
The structure supporting the motor and gear reduction device includes a motor housing wall 13 associated with the housing 1 and located between the motor and the speed reduction device. Bearings 14 through 17 mount the appropriate shafts as indicated in FIG. 1. The bearings are mounted in the motor housing 1, the motor housing wall 13, a housing 18 for the speed reduction device and a housing wall 19 for the speed reduction device positioned against the housing wall 13 of the motor housing.
The typical motor driven gear reduction device as illustrated in FIG. 1 has the ability to accomplish a large reduction ratio by increasing the number of gear wheels. However, the size of the unit is substantial and increases with desired reduction. The number of parts and the gearing losses increase by increasing the number of gears to achieve greater reduction. When the number of gear teeth is increased to achieve a larger reduction ratio, the size of the unit again increases. Thus, conventional construction provides constraints on compactness, weight, complexity and the like.